1. Field of the Invention
The present invention relate to apparatus and method for delivering a source reagent material in vapor form to a substrate element in a CVD reactor for deposition on the substrate.
2. Description of the Related Art
In the technology of chemical vapor deposition (CVD), it has been common practice to utilize in various applications a wide variety of precursor (source reagent) compositions containing the component to be deposited on the substrate in the chemical vapor deposition reactor. Numerous techniques are known for carrying out CVD. By way of example, U.S. Pat. No. 5,225,561 issued to Peter S. Kirlin et al. discloses CVD source reagents for the formation of high temperature superconductor films including various .beta.-diketonate complexes of barium, strontium, and calcium, and U.S. Pat. No. 5,204,314 issued to Peter S. Kirlin et al. discloses apparatus and method for flash vaporizing source reagents of involatile character and depositing the metal or other component of such source components in the downstream CVD reactor joined in flow communication to the flash vaporization delivery system.
Many chemical vapor deposition and dry etching processes require uniform dispersal of gases. Such dispersal may be effected by a "showerhead"-type device, featuring a multiplicity of gas discharge passages in a face or discharge surface of such device.
Among the vapor phase species utilized in CVD processes, many source reagents maintain their physicochemical character (not decomposing or condensing) only if they are maintained in a narrow range of temperatures.
This is particularly true of many low volatility CVD precursors. For such source reagents, the temperature criticality is particularly challenging to the operation of the CVD process when the heated substrate (on which the deposition is to take place) is in close proximity to the showerhead discharge surface and the substrate has a high "view" factor for the showerhead discharge surface. In these circumstances, the showerhead may be readily driven to unacceptably high temperatures by radiated and convective energy in the process system, which may be on the order of kilowatts in magnitude.
Accordingly, it would be a substantial advance in the art, and is an object of the present invention, to provide an improved showerhead-type dispersing structure for discharging vaporized source reagents to a substrate or other deposition locus in a chemical vapor deposition reactor.
It is another object of the invention to provide such showerhead-type dispersing structure which is capable of being operated in a closely controllable selected temperature range, so that the dispersed CVD source reagent is not heated to temperatures at which the reagent is susceptible to decomposition or degradation.
It is another object of the invention to provide a corresponding method of dispersing CVD source reagents in vapor form, in a manner maintaining the physicochemical stability of such reagents, to carry out the CVD process without the occurrence of substantial degradation or decomposition of the source reagent material.
Other objects and advantages of the invention will be more fully apparent from the ensuing disclosure and appended claims.